Ethnic inequities in health: Have we made progress? Pertussis mortality and morbidity in New Zealand for Māori and non-Māori over the past century

Abstract

Aim: To measure the incidence of pertussis in New Zealand and compare the rates of this disease in the Māori and non-Māori populations. Methods: All available mortality, hospitalisation and notification data relating to pertussis in New Zealand was collected. This spanned time frames from 1872 to 2013, with the time frames where data were available differing for mortality, hospitalisation and notification data. Results: Pertussis has always been a serious costly disease in New Zealand, associated with significant morbidity, and almost all serious pertussis disease occurs in those aged less than 1 year of age. Records have always shown that there is an ethnic difference in pertussis disease burden in New Zealand. Initially Māori had a significantly higher mortality rate from pertussis than non-Māori. Hospital discharge data since 1988 shows Māori have significantly higher hospitalisation rates for pertussis and the ethnic differences in hospitalisation rates are not decreasing. Non-Māori have higher rates of notification of pertussis than Māori. Māori rates of vaccination have always been significantly lower than rates in non-Māori. Although ethnic differences in immunisation coverage at age 2 years have disappeared in 2014 they remain wide at age 6 months, indicating that immunisation timeliness is poorer for Māori compared with non- Māori. Conclusions: Compared with non-Māori, Māori experience a greater burden of severe pertussis disease, i.e. that resulting in death or hospital admission. The long term persistence of an ethnic difference in pertussis disease burden in New Zealand means that it is now, like other ethnic differences, established and accepted as normal in New Zealand. Unlike many other ethnic differences there is a single solution. On-time administration of the pertussis vaccination prevents pertussis disease. If Māori children received on-time administration of vaccines at the same rate as non-Māori the ethnic difference in pertussis would be expected to disappear. Achievement of equitable on-time administration of vaccines to at risk populations will require a purposeful change in the way vaccines are administered to at risk populations. If ethnic differences are maintained by systemic factors a substantial attitudinal change and determined effort is required to address these.